The job market is an elusive, constantly shifting thing. Yet, for all that, as this map that takes us through the last 3 and a half decades of jobs in America shows, there are some fascinating patterns —and one clear choice for the single most common job in all of America right now.

The map is the work of Quoctrung Bui over at Planet Money, and it uses Census data from the last 36 years to determine which single job in each state the largest number of its residents were working at. Looking at the map as it approaches our own time, it's clear that truck driver is far away the most common job to hold.

Why is that? It's for a couple reasons, explains Bui. For one thing, it's a job that resists any attempts at outsourcing or automation, but just as important is how the Census Bureau classifies it:

The prominence of truck drivers is partly due to the way the government categorizes jobs. It lumps together all truck drivers and delivery people, creating a very large category. Other jobs are split more finely; for example, primary school teachers and secondary school teachers are in separate categories.

You can check out the full list of occupations by year and get a closer look at the map over at NPR.